fix(task_sync): defend against silent sync_id integrity violations

The cross-instance sync silently drops tasks when x_fc_tech_sync_id is
missing on the technician, and silently collapses duplicates via dict
comprehension. Both make sync break in ways that are invisible until
someone notices a missing task on the other instance.

- _get_remote_tech_map / _get_local_syncid_to_uid: warn on duplicates
- _push_tasks_to_remote: info-log when a task is skipped because the
  tech has no sync_id or no remote counterpart
- res.users onchange: warn in the form when entering a sync_id that
  is already used by another active field staff

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_tasks/__manifest__.py

@@ -4,7 +4,7 @@
 
 {
     'name': 'Fusion Tasks',
-    'version': '19.0.1.0.0',
+    'version': '19.0.1.1.0',
     'category': 'Services/Field Service',
     'summary': 'Technician scheduling, route planning, GPS tracking, and cross-instance sync.',
     'author': 'Nexa Systems Inc.',

fusion_tasks/models/res_users.py

@@ -2,7 +2,7 @@
 # Copyright 2024-2026 Nexa Systems Inc.
 # License OPL-1 (Odoo Proprietary License v1.0)
 
-from odoo import models, fields
+from odoo import models, fields, api
 
 
 class ResUsers(models.Model):
@@ -24,3 +24,26 @@ class ResUsers(models.Model):
              'Must be the same value on all instances for the same person.',
         copy=False,
     )
+
+    @api.onchange('x_fc_tech_sync_id')
+    def _onchange_x_fc_tech_sync_id_dup_warning(self):
+        if not self.x_fc_tech_sync_id:
+            return
+        dup = self.env['res.users'].sudo().search([
+            ('id', '!=', self._origin.id or self.id),
+            ('x_fc_tech_sync_id', '=', self.x_fc_tech_sync_id),
+            ('x_fc_is_field_staff', '=', True),
+            ('active', '=', True),
+        ], limit=1)
+        if dup:
+            return {
+                'warning': {
+                    'title': "Duplicate Tech Sync ID",
+                    'message': (
+                        f"Tech Sync ID {self.x_fc_tech_sync_id!r} is already used "
+                        f"by {dup.login} ({dup.partner_id.name}). Cross-instance "
+                        f"task sync only routes to ONE user per sync ID — "
+                        f"pick a unique value or only one tech's tasks will sync."
+                    ),
+                }
+            }

fusion_tasks/models/task_sync.py

@@ -135,11 +135,18 @@ class FusionTaskSyncConfig(models.Model):
         ], {'fields': ['id', 'x_fc_tech_sync_id']})
         if not remote_users:
             return {}
-        return {
-            ru['x_fc_tech_sync_id']: ru['id']
-            for ru in remote_users
-            if ru.get('x_fc_tech_sync_id')
-        }
+        by_sync_id = {}
+        for ru in remote_users:
+            sid = ru.get('x_fc_tech_sync_id')
+            if not sid:
+                continue
+            if sid in by_sync_id:
+                _logger.warning(
+                    "Task sync: duplicate x_fc_tech_sync_id %r on remote %s "
+                    "(uids %d and %d) — only the last seen will be reachable",
+                    sid, self.name, by_sync_id[sid], ru['id'])
+            by_sync_id[sid] = ru['id']
+        return by_sync_id
 
     def _get_local_syncid_to_uid(self):
         """Build {x_fc_tech_sync_id: local_user_id} for local field staff."""
@@ -148,7 +155,16 @@ class FusionTaskSyncConfig(models.Model):
             ('x_fc_tech_sync_id', '!=', False),
             ('active', '=', True),
         ])
-        return {u.x_fc_tech_sync_id: u.id for u in techs}
+        by_sync_id = {}
+        for u in techs:
+            sid = u.x_fc_tech_sync_id
+            if sid in by_sync_id:
+                _logger.warning(
+                    "Task sync: duplicate x_fc_tech_sync_id %r locally "
+                    "(uids %d and %d) — only the last seen will be reachable",
+                    sid, by_sync_id[sid], u.id)
+            by_sync_id[sid] = u.id
+        return by_sync_id
 
     # ------------------------------------------------------------------
     # Connection test
@@ -219,9 +235,15 @@ class FusionTaskSyncConfig(models.Model):
         for task in tasks:
             sync_id = local_map.get(task.technician_id.id)
             if not sync_id:
+                _logger.info(
+                    "Task sync: skipping task %s — technician %s has no x_fc_tech_sync_id",
+                    task.name, task.technician_id.login or task.technician_id.id)
                 continue
             remote_tech_uid = remote_map.get(sync_id)
             if not remote_tech_uid:
+                _logger.info(
+                    "Task sync: skipping task %s — sync_id %r has no matching tech on %s",
+                    task.name, sync_id, self.name)
                 continue
 
             # Map additional technicians to remote user IDs